MEMS micro-mirrors have been widely explored and used for optical switching and attenuation applications. The most commonly used application of a MEMS micro-mirror device being optical cross-connect switching. In most cases, individual micro-mirror elements are used to ‘steer’ a beam (i.e., an optical channel) to a switched port or to deflect the beam to provide attenuation on a channel-by-channel basis. Consequently, if the system is designed for a particular ‘wavelength plan’—e.g. “X” number of channels at a spacing “Y”, the system is not ‘scalable’ to other wavelength plans.
Further, dynamic gain equalization (or “flattening”) is a critical technology for deployment of next-generation optical network systems. Dynamic gain equalization filters (DGEF's) or Dynamic gain-flattening filters (DGFF's) function by adding varying amounts of attenuation at different wavelengths in the signal spectrum of optical fiber communication systems to equalize the power at each wavelength. For instance, a DGEF may be designed to operate in the “C-band” (˜1530–1565 nm) of the communication spectrum by being able to selectively attenuate spectrally concatenated “bands” of some pre-selected spectral width (e.g., 3 nm). The total number of bands within the operating range of a DGEF is determined by the width of each individual band.
A method of attenuating or flattening a WDM signal is to spatially separate different wavelengths, channels or wavelength bands using bulk diffraction grating technology, as is known in spectroscopy. For example, each channel of a DGEF is mapped to a different location on a generic micro-electro-mechanical system (MEMS) device, whereby each channel or band of channels is appropriately attenuated to flatten or equalize the output signal. The MEMs device, although discussed as a DGEF may also embody a DGFF, may be composed of a series of tilting mirrors, wherein each discrete channel hits near the center of a respective mirror and does not hit the edges. In other words, one optical channel reflects off a single respective mirror.
The MEMs-based DGEF that has one mirror for each optical channel are very sensitive to calibration and alignment. They are also sensitive to environmental changes, such as shock, vibration and temperature changes. Further, these DGEFs are not wavelength plan independent. In other words, a DGEF for compensating a WDM signal having 50 GHz spacing cannot compensate a WDM signal having 25 GHz spacing without having to alter the optical components or recalibrating the device.